The following relates to printing systems. It finds particular application to tracking, predicting, and preemptive scheduling of jobs by monitoring the impending anticipated process control protocols or routine maintenance schedules of individual printing system components and accordingly altering or overriding the protocols of the individual printing system components available to process and schedule jobs.
In a typical xerographic system, such as a copying or printing device, an electronic image is transferred to a print medium, such as paper, plastic, velum and the like. In a xerophotographic process, a photoconductive insulating member is charged to a uniform potential and exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates an electrostatic latent image on the member, which corresponds to the image areas contained within the document. Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with developing powder referred to in the art as toner. This image may be transferred to a support surface, such as paper, to which the toner image is permanently affixed in a fusing process.
In a multicolor electrophotographic process, successive latent images corresponding to different colors are formed on the insulating member and developed with a respective toner. Each single color toner image is transferred to the paper sheet in superimposed registration with the prior toner image. For simplex printing, only one side of a sheet is printed, while for duplex printing, both sides are printed. Other printing processes are known in which the electronic signal is reproduced as an image on a sheet by other means, such as through impact (e.g., a type system or a wire dot system), or through use of a thermosensitive system, ink jets, laser beams, or the like.
A conventional approach to increasing printing throughput is to increase the speed of the printer. However, increasing printer speed typically results in greater stress on the individual components of the printer. Another approach is to employ several marking engines, which can be vertically and/or horizontally stacked, within a printing platform. Multiple marking engine systems provide relatively higher overall output by parallel printing processes, wherein portions of the same document are printed on multiple printers or concurrently processing multiple print jobs. For example, an electronic print job that includes color and monochrome portions may be partitioned and distributed across color and monochrome printers. Print media substrate (e.g., paper, velum, plastic . . . ) is fed from a common or different source to the printers. Printed substrate is conveyed to a finisher where the media associated with a single print job are assembled. Such systems are commonly referred to as “tandem engine” printers, “integrated parallel” printers, or “cluster printing” printers.
In a conventional single engine system, when a print engine is disabled or scheduled for process control protocols/routine maintenance, the system shuts down. During periods of down time, print jobs are delayed, which results in customer annoyance, decreased customer utility, and loss in revenue. This problem is exacerbated when considered in light of a population of printing platforms. With a conventional multi-engine system, a faulty or unavailable print engine is by-passed. Print jobs associated with the unavailable print engine are re-routed to one or more available print engines. In U.S. Pat. No. 5,150,167, by Gonda, et al., and entitled “Image Forming Apparatus,” print jobs are re-routed in order to maintain continuous printing operation. However, Gonda, et al. merely determines whether a printer is able to continue processing an on-going print job based on lack of paper, low toner, etc. If not, the print job is routed to another printer that is associated with a tray with paper, a cartridge with toner, etc. In addition, simply by-passing an unavailable print engine reduces processing performance, overall throughput, and causes out of sequence print runs which can result in purging of print jobs or partial print jobs.